The present invention relates to a device for producing effect yarns on process machines through the deliberate production of short lumps in the yarn through short-duration yarn overfeed.
Individuality in the design of textiles is ever-more frequently determining the development of special and high-quality finished yarns. In the area of process machines, particularly in the case of air and false-twist texturing machines, effect yarns are assuming increasing importance in yarn finishing. Different methods and different machines are known for the production of effect yarns, although the fundamental principle for the short lumps in the yarn, termed slubs, is always the same. Filament yarns are tied into the air texturing nozzle or false-twist zone, through short-duration overfeed according to predefined formulas, in such a way that fine or intensive structure effects are produced. Due to the yarn overfeed, the resultant slubs have a greater yarn cross section and have a typical length of between 20 and 100 mm. The slubs can be varied according to the magnitude and duration of the increased overfeed. The spacing of the slubs is controlled by the time interval between the overfeeds. To date, this method has only been applied to air texturing machines, but application to false-twist texturing is also conceivable.
Presently, two types of unit are used for producing effect yarns, the HemaSlub method developed and marketed by Heberlein AG, and an even older system which uses a yarn deflection lever which controls the overfeed through a periodic movement. The HemaSlub device is a feed mechanism, which can be integrated into the air-jet texturing process, with electronically controlled pressure rollers and an effect yarn generator. This feed mechanism can be mounted on different machines and is simple to operate, but it is relatively elaborate and costly, and can only be used in a yarn line with unheated godets. The older system with the yarn deflection lever, while simple and cost effective, has only a limited application since only relatively small yarn deflections are possible.
The object of the present invention is to provide a device for producing effect yarns which is cost effective and simple to install, the use of which makes it possible to retain not only the standard yarn line with unheated godets but also that with heated godets. This object is achieved, according to the present invention, by a device for lateral yarn deflection, which comprises a motor-driveable, servo-controlled yarn guide with an adjustable stroke. Movement of the yarn guide in one direction effects a slight underfeed, and movement in the other direction effects a pronounced overfeed of the yarn.
In a preferred embodiment of the device according to the invention, the yarn guide is attached to a traverse-motion element, preferably by a wire rope, a string or a belt. The traverse-motion element is formed by a flexible member which is rigid in the stroke direction by which it is driven. This embodiment is of the type of the yarn transfer devices, described in EP-A-0 453 622 and EP-A-0 829 444, for winding a yarn on to a bobbin. Since this system has a very small mass, very steep flanks of the slubs can be achieved. In addition, due to the high dynamics, high yarn speeds can be achieved. Since the drive system is servo-controlled, it is also possible for almost any acceleration and speed profiles to be achieved.
In another preferred embodiment of the device according to the invention, the yarn guide is formed by a lever which can be driven in an oscillating manner, or is disposed on such a lever. This preferred embodiment, can be of the type of the yarn transfer device described in U.S. Pat. No. 5,908,170, which is incorporated herein by reference. It is particularly suitable for short slubs because the stroke of the lever is naturally smaller than that of the traverse-motion element formed by a flexible member.
In another preferred embodiment of the device according to the invention, the yarn guide effects the storage of a yarn length, in the form of a loop, which corresponds to the desired overfeed. And in a related preferred embodiment of the device according to the invention, when the stored yarn length is released, the drive of the yarn guide is controlled in relation to the volume and length of the slub to be produced.
In yet another preferred embodiment of the present invention, after production of a slub, the yarn guide is driven as slowly as possible when returned into the deflection position for the next overfeed.
The present invention also relates to the use of the aforesaid device on a false-twist texturing machine. In this instance, the device for the lateral yarn deflection is preferably disposed in the yarn line immediately before the inlet of the heating element of the machine.
The present invention also relates to the use of the aforesaid novel device on air texturing machine. Here, the device for lateral yarn deflection is preferably disposed directly before the air-jet texturing nozzle.